Disorders of the upper extremity caused by repeated trauma are the most common occupational illness in the United States and result in substantial disability, lost wages, and personal suffering. Carpal tunnel syndrome is often considered prototypic of these disorders. Unfortunately, the methods currently available for diagnosing carpal tunnel syndrome are inadequate for use in occupational epidemiologic studies of this disorder. Consequently, studies of occupationally-related carpal tunnel syndrome have typically relied on symptoms or physical finding as the sole measures of disease outcome. Likewise, few studies assessing the long-term effectiveness of treatment of carpal tunnel syndrome have utilized quantitative measures. A non-invasive testing method used to study other neuropathies, quantitative vibrotactile threshold determination, may be useful for attaining rapid, painless, and reliable diagnoses of carpal tunnel syndrome. At this time, however, appropriately designed, powerful validation studies of this method in well-defined patient populations have not been performed. A cross-sectional study designed to estimate the sensitivity and specificity of this method for diagnosing carpal tunnel syndrome is proposed. Three groups will be studied: one electrophysiologically- proven to have carpal tunnel syndrome, one with carpal tunnel like symptoms but with normal electrophysiologic test results and one asymptomatic group with normal electrophysiologic tests. All subjects will be evaluated with symptoms review, physical examination, and vibrotactile threshold measurement. Of special interest is the potential for improvement in sensitivity that voluntary wrist flexion may have on the vibrotactile threshold measure. The specificity of vibrotactile threshold parameters will be defined from the disease-negative groups. Sensitivity will be defined as the proportion of disease-positive subjects whose measures exceed those values. A longitudinal assessment of subjects treated for carpal tunnel syndrome will also be performed. The electrophysiologic and vibrotactile outcomes that correlate best with changes in symptoms will be identified. In addition, the symptom-free group will be studied serially to establish the normal range of threshold variability over time. Vibrotactile threshold testing may be sensitive and specific method of diagnosing carpal tunnel syndrome. If proven useful, it could be incorporated into epidemiologic studies that are currently limited to use of relatively nonspecific symptoms and signs or uncomfortable and expensive electrophysiologic measures for diagnosis.